The present invention relates to the textile industry and more particularly to an improvement in shuttleless looms in which the weft is inserted from feed bobbins (or like supports) situated outside the shed.
Such looms use different types of means for inserting the weft into the shed, such as for example: jets of fluid, nozzles or throwing members with gripping means, the kinetic energy of the weft yarn, etc.
In most of these looms, the weft yarn to be inserted is prepared beforehand into lengths or picks corresponding to the wanted machine width and stored successively in a reserve member before being inserted into the shed.
In all these looms, the main problem arising is that of the re-introduction of the end of the cut weft into the reserve member. This problem which is already known to arise in looms using only one type of weft yarn (production of plain woven fabrics) is amplified in multiweft looms used in the production of fancy fabrics and requiring the insertion, according to a predetermined sequence, of weft yarns of different color and/or nature.
It is the object of the present invention to solve the aforesaid problem.
In the description given hereinafter, the invention is applied to shuttless looms in which the weft is inserted into the shed formed by the warp yarns according to the technique known as "insertion-by-inertia" and which is described for example in published French Pat. Nos. 2 477 587 (corresponding to U.S. Pat. No. 4,509,563) and 2 495 196 (corresponding to U.S. Pat. No. 4,479,518). This of course is not in any way restrictive, and the invention may also be applied to any other weaving technique where similar problems may arise.
In general, said throwing-by-inertia technique, according to which the weft yarn is thrown into the shed in the form of a loop which unwinds, implies the preparation of the weft length before this is thrown. Said preparation consists in accumulating a metered length of yarn in a reserve situated between the yarn supply source (bobbin) and the side of the machine where the weft is due to be inserted, and then extracting the yarn from said reserve when it is about to be thrown. As described in the two aforesaid patents, extraction from the reserve can be carried out through the same channel as that through which the yarn was introduced, but in reverse. This therefore, necessarily implies a change of path for the yarn during those displacements, first from the metering-delivering device to the reserve, and second, from the reserve to the throwing member throwing the yarn in the direction of the shed.
This necessity is obvious from the teachings of French Pat. No. 2 477 587 (corresponding to U.S. Pat. No. 4,509,563). According to the solution described in that document, the change of path takes place without any special guiding, the yarn being thrown freely from one point to another to be thereafter deviated in another direction. This technical solution is very satisfactory but it is difficult to perform considering that the yarn passes freely close to the throwing member and that in that area, perturbing air streams may occur, especially when the throwing member is of the type with rotating impellers. Indeed, the position of the yarn may be deviated and the gripping of said yarn by the throwing member may be perturbed.
French Pat. No. 2 538 008 (corresponding to U.S. Pat. No. 4,544,001) describes a solution which makes it possible to overcome the aforesaid disadvantages, and which, in general, consists, as in fact mentioned in French Pat. No. FR 2 506 795, in placing the end of the yarn which has just been cut in a held over position, between the metering-delivering device and the storage means. Said cut end of the yarn is placed in said held-over position in the area extending between the inlet into the reserve and the outlet from the delivering device, by guiding channels which, if necessary, can be extended as far as close to the scissors for cutting the yarn on the selvedge of the material. With a loop permitting the insertion of various wefts according to a predetermined sequence, it is necessary to have as many channels as there are yarns in order to place said yarns in the held-over position before re-inserting them into the reserve. It should also be noted that in such a case, if the object is to make the holding-over circuits pass near the scissors in order to reduce the length of the yarn to be drawn out, then it is necessary to lengthen and to bend the circuits, hence a very complex construction. Certainly, this problem may be overcome in the end, as can be seen from the examples illustrated in FIGS. 7 and 8 of the aforesaid patent by placing said circuits aslant, but then, the part of the circuit situated at the outlet from the reserve and placed in facing relationship to the throwing rollers gripping line is at a distance from said line which is aslant, this impairing the firmness of the gripping during the actual throwing operation.
Finally, in all cases, when the weft yarn is reintroduced into the reserve, the cut end is re-introduced first into said reserve, generally under the action of an air stream which pushes the yarn, and entangling or bundling up of said end may occur, or generally, the cut end takes on a more or less sinuous form which perturbs the sequencing and the withdrawal of the yarn from the reserve for the throwing operation.
The present invention eliminates these drawbacks and relates to an improved method, applicable not only in the case of one-color looms, but also in the case of multi-color looms, and to a device for carrying out said method.
In general, the invention relates to an improvement in the process for inserting yarn lengths into the shed of a loom, wherein a metering-delivering device supplies a storage member in which a predetermined length of yarn is stored, said yarn length being caught in the interval between the delivering device outlet and the storage member, in order to be inserted into the shed formed by the warp yarns, then said yarn length is gripped close to the selvedge of the fabric and cut, the cut end of the yarn being held over before being re-introduced once again into the storage member for the next insertion, said improvement being characterized in that the cut end of the yarn is held over in an independent circuit outside the path connecting the outlet of the metering device and the inlet of the reserve, re-introduction of the yarn into the reserve being performed so that the cut end is reintroduced as a loop which unwinds from a fixed point at the outlet of the delivering device to the inlet of the reserve under the action of an air stream, and the weft yarn being subjected to the action of the delivering device only after it has completely unwound and stretched under the action of a nozzle.
According to this process, the end of the yarn, released after the cutting operation, is firmly held and guided throughout the whole phase of re-introduction into the reserve. Moreover, said process is particularly well adapted to be used with multi-weft looms, where the wefts are kept separate one from the other outside the throwing phase.
In summary, in the process according to the invention, after the cutting operation, the free end of the yarn is kept in a holding over circuit, and during the re-introduction, before the start of the metering phase, said free end is carried towards the reserve by means which exert a pulling action from a fixed point downstream of the metering device, this helping the cut end to enter evenly into the reserve.
The invention also relates to a device for carrying out said process, which device is essentially characterized in that temporary storage means (holding over channel) for the cut end of the yarn are provided between the outlet of the metering-delivering device and the cutting member close to the selvedge, and this outside the path followed by the yarn, on the one hand, between the metering device and the reserve, and on the other hand, when the yarn is thrown from the reserve into the shed, said means keeping the yarn in stretched condition under the action of an air stream, before it is introduced into the reserve under the action of the metering device.
If the invention is applied to a one-color loom, the storage member is situated inside the throwing plane, whereas if the invention is applied to a multi-color loom, there must be as many storage members as there are weft lengths to be inserted, said storage members being so oriented as to to guide the yarn within a plane cutting through the throwing plane, the yarns being then stored in n planes converging towards the throwing plane.